1. Field of the Invention
The invention relates to a controller for a diesel engine and a method of controlling a diesel engine, in which fuel injection control is performed.
2. Description of the Related Art
In a diesel engine, fuel injected into a combustion chamber by an injector is compressed and ignited after a certain period of time has elapsed since the injection, that is, after an ignition lag has elapsed since the injection. In order to improve the engine power and the emission of diesel engines, a controller that controls fuel injection timing, the amount of fuel injection, etc. based on the operational status of the engine with such ignition lag taken into consideration is widely used (see Japanese Patent Application Publication No. 2001-152948, for example).
With regard to the fuel used in diesel engines, the lower the cetane number is, the longer the ignition lag is. Thus, even when the optimum fuel injection timing and the optimum amount of fuel injection are set based on a given standard cetane number by the time the diesel engine is shipped, for example, if a fuel, such as a winter fuel, that has a lower cetane number is supplied to the fuel tank, the fuel ignition timing is retarded and the combustion condition is deteriorated, which can lead to misfiring in the worst case. In order to suppress the occurrence of such a problem, it is preferable that the fuel injection timing, the amount of fuel injection, etc. be adjusted based on the cetane number of fuel. Note that in order to suitably perform such adjustment, it is necessary to accurately estimate the cetane number of fuel.